They would get into some of the usual shenanigans that teen wood sprites enjoy. Nighttime flying, races through the trees, and the like. At that point, Cerul would also have been training his skills with the Voice and Scar would be training to become a knight. They had some prestigious goals ahead of them, but they found a way to be troublemakers despite this.
Their backgrounds are very different, but they’ve been best friends for a long time, maybe because of their differences. Scar is hotheaded and brash, and Cerul’s level calm is a really good contrast to him. They keep each other from going too extreme in either direction.
To name a specific incident in their younger years, once they decided they were going to agitate a bluejay. They ended up getting chased for at least a mile by the thing and Cerul nearly sprained a wing getting away.
You can bet they got their ears pinched once they made it home after that.